Tuesday, December 1, 2009

Long-awaited research findings just published identify one possible mechanism responsible for accelerated steel corrosion in the Duluth-Superior harbor. The peer-reviewed paper published in CORROSION, The Journal of Science and Engineering, outlines a study led by Brenda Little, Senior Scientist, Marine Molecular Processes, Naval Research Laboratory, Stennis Space Center. The study was supported by the U.S. Army Corps of Engineers, Detroit District, and the Duluth Seaway Port Authority.

The press release goes on to say, "In layman’s terms, conclusions of this study describe the process by which specific iron-oxidizing bacteria attach to carbon steel, creating a “nodule” of biomass and corrosion products. Conditions beneath those nodules (i.e. “tubercles”) cause copper dissolved in harbor water to precipitate and adhere to the iron. When ice chunks scrape against those pilings each winter, the tubercles break, exposing the copper-covered iron to oxygen which, in turn, causes the steel in those pitted areas to corrode at a faster rate…creating an almost “Swiss cheese” effect in nearly 14 miles of steel pilings and dock walls along the Duluth-Superior waterfront."

Local participants in the work in Duluth Harbor include Gene Clark, specialist with Wisconsin Sea Grant and Dale Bergeron from Minnesota Sea Grant.